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Solstice and Equinox/Transcript
Transcript Text reads: The Mysteries of Life with Tim and Moby A boy, Tim, is sitting on a desert island. There is a laptop computer on the sand in front of him and a world map on a stand behind him. Tim is writing in a small notepad. TIM: Tim's log. March 20th. Still here on this tiny island at the equator, located at 0 degrees latitude. On Tim's map, an arrow at the equator is labeled: Tim. An arrow pointing at the northeast region of the United States is labeled: Cassie and Rita. An arrow pointing at the North Pole is labeled: Moby. TIM: The time-lapse camera I set up this morning is recording the sun's path across the sky. A camera next to Tim is pointed at the sky. TIM: Cassie and Rita are doing the same thing at 40 degrees North latitude. An image shows two girls, Cassie and Rita, camping in the woods. They have a camera set up in the same way Tim does. TIM: And Moby's hanging out at 90 degrees latitude, at the North Pole. An animation shows a robot, Moby, standing next to an igloo at the North Pole. It is snowing. Moby has a camera set up in the same way Tim, Cassie, and Rita do. MOBY: Beep. TIM: All this to answer a letter. Tim reads a typed letter. TIM: Dear Tim and Moby, What do solstices and equinoxes have to do with the seasons? From, Abby. TIM: The four seasons are caused by the tilt of the Earth as the planet orbits the sun. An animation shows Earth orbiting the sun. The Earth is tilted, as Tim describes. TIM: This tilt makes sunlight hit the Northern and Southern hemispheres at different angles during Earth's year-long journey around the sun, causing the changes in temperature and amount of daylight that define the seasons. The animation illustrates how the amount of sunlight that hits the Northern and Southern Hemispheres changes as Earth orbits around the sun, rotating on its axis. TIM: Four times a year, Earth reaches special points in its orbit where its axis of rotation lines up perfectly with the sun to produce some really cool effects. The animation illustrates the four points in Earth's orbit that Tim describes. Two of them, illustrate times when the sun's light is hitting exactly half of the Earth. The other two, illustrate times when the sun's light is focused on either the Northern or Southern hemisphere. TIM: And today is one of those times. The animation focuses on one of the points where half of the Earth is illuminated. TIM: In the Northern Hemisphere, March 20th or 21st is the vernal equinox, the first day of spring. Right now, the Earth's axis is perpendicular to the sun's rays. Both hemispheres are the same distance from the sun, which means they're both receiving the same amount of sunlight. The animation illustrates Earth's position as Tim describes it. Exactly half of the globe is illuminated by the sun's light. The separation between light and dark halves runs directly along the line of Earth's axis. TIM: This will happen again in six months, around September 22nd or 23rd, at the Northern Hemisphere's autumnal equinox, the first day of fall. Earth moves to the other side of the sun to illustrate what Tim is describing. MOBY: Beep. TIM: Good point, Moby. When it's the vernal equinox in the Northern Hemisphere, it's the autumnal equinox in the Southern Hemisphere, and vice versa. Images compare a spring scene in the Northern Hemisphere with an autumn scene in the Southern Hemisphere. TIM: In other words, the seasons are opposite in the Northern and Southern Hemispheres. During an equinox, the sun looks like it's moving directly over the equator. Here at the equator, the sun rises straight up in the east; reaches the zenith, the highest point directly overhead; and sets straight down to the west. An animation shows the sun rising in a perfectly vertical path over the ocean, moving across the sky as Tim describes, and setting over the ocean in the same way. TIM: As you go farther north, the sun's arc is lower in the sky. An animation shows the sun over a wooded northern region. It is lower in the sky than it was over Tim's island. TIM: And way up at the pole, the arc is pretty much flat on the horizon! An animation shows the Sun as seen from the North Pole. It moves horizontally as Tim describes. TIM: Except for the poles, every place on Earth gets 12 hours of day and 12 hours of night, which explains the word equinox. It comes from the Latin words aequus, meaning equal, and nox, meaning night. An image shows a star-filled night sky. Text on the image reads: equinox. The text changes to illustrate the origin of the word as Tim describes it. TIM: After the vernal equinox, the Northern Hemisphere points more and more toward the sun. An animation of Earth and the Sun shows the positioning Tim describes. The area of the sun's light moves up into the northern part of the globe. TIM: From where Cassie and Rita are camped out, the Sun's arcs get longer and higher, which gives us hotter days and more daylight! An animation shows the sun over the same wooded region as earlier. The sun is higher in the sky than it was before. TIM: About three months from now, on June 21st or 22nd, we'll have the longest day of all in terms of sunlight: the summer solstice. That's when the Northern Hemisphere is pointed almost directly at the sun. It's the first day of summer and the farthest north the sun rises and sets during the year! The animation of Earth and the sun illustrates what Tim describes. TIM: After that, the sun will start rising and setting more and more to the south. Earth moves to another spot in its orbit to illustrate what Tim describes. TIM: The days get less and less daylight, and, as we pass the autumnal equinox, colder. The animation of the wooded region now has trees with autumn colors. The sun is also lower in the sky than before. TIM: Finally, on December 21st or 22nd, we'll have the day with the least amount of sunlight: the winter solstice, where the Northern Hemisphere is pointed as far away from the sun as it can get. The animation of the Earth and sun illustrates what Tim describes. TIM: This is the first day of winter, and the farthest south the sun will rise and set. Where Cassie and Rita are at, summer daylight can be as long as 16 hours, while winter daylight can be as short as 8 hours. Cassie and Rita are standing in the woods with their camera pointed at the sky. It is dark, cold, and snowing. They bundled up in winter jackets and shivering. TIM: Here at the equator, where the tilt of Earth's axis doesn't affect the sun's path as much, daylight stays pretty close to 12 hours all year round. But the tilt has a huge effect at the poles. The animation of Earth and the sun's light illustrates how sunlight hits the equator the same amount no matter the season. TIM: The pole facing the sun gets six straight months of daylight, while the pole facing away from the sun gets six straight months of darkness! MOBY: Beep. Moby's North Pole location is in darkness. He flips on a flashlight and sees a polar bear glaring at him. TIM: Oh, the word solstice comes from the Latin words sol, meaning sun, and sistere, meaning to stand still. An image shows a star-filled night sky. Text on the image reads: solstice. The text changes to illustrate the origin of the word as Tim describes it. TIM: Throughout the year, the sun's path through the sky keeps shifting either north or south, right up until the solstices, where it seems to stand still for a moment before shifting back in the opposite direction. MOBY: Beep. Moby, at the North Pole, beeps at Tim, on the island's beach, over Tim's laptop. TIM: Yeah, humans have paid attention to this stuff for thousands of years. Ancient civilizations timed their farming and hunting to the changing seasons! An image shows an ancient cave painting of humans hunting deer. The painting includes the sun, high in the sky. TIM: That's why solstices and equinoxes became important dates for celebrations and holidays in so many cultures! MOBY: Beep. Again, Moby beeps from Tim's laptop. Tim looks at his laptop screen. The screen shows Moby dressed as Santa Claus, in front of an igloo at the North Pole. It is snowing. TIM: Um, it's about one equinox and two solstices too early for that one. Category:BrainPOP Transcripts